Within the electronic industry, different kinds of electronic apparatuses of the above type are provided. Within particular fields of the electronic industry, electronic apparatus are provided in which various electronic circuits are included which require shielding from each other and from the environment or surroundings. An example of such a field is the telecommunication field, particularly the radio communication field.
In accordance with the commonly employed shielding technique the individual electronic circuits are shielded from each other and from the environment or surroundings in individual metallic encasings. In one embodiment of this circuit encasing technique, the individual electronic circuits are provided on separate circuits boards, such as printed circuit boards, e.g. single or double-sided printed circuit boards, which are enclosed within individual metallic encasings or housings. However, as the electronic industry is moving towards a miniaturizing of the electronic circuits, involving the technique of providing integrated circuits and further involving the well-known layer techniques, including thick-film technique and thin-film technique, the provision of the individual electronic circuits to be shielded from one another and from the environment or surroundings on separate circuit boards and arranging the individual circuit boards within individual metallic encasings is considered to be an irrational technique which to a great deal counteracts the miniaturizing and integration trend.
In order to solve the problem of combining the miniaturizing and integration technique and the shielding requirements of the electronic circuits which are to be shielded, it has been suggested to arrange the electronic components together constituting the electronic circuits of the apparatus on a single circuit board and to provide shielding of individual electronic circuits in relation to one another and in relation to the environment or surroundings.
In Swedish Pat. No. 75 108 00-1 (publication No. 391 105) the provision of shielding plates is disclosed which are soldered on to the circuit board together with the electronic component and which together define compartments in which the individual electronic circuits are encased. The circuit board including the electronic components and the shielding plates is arranged within the inner space of the apparatus housing which serves the purpose of shielding the electronic circuits in relation to the environment or surroundings. However, this technique is not quite satisfactory since the technique involves the provision of a great number of individual components, viz. the individual shielding plate, which are to be mounted and soldered on to the circuit board. Furthermore, the shielding plates have to provide electrical contact with the apparatus housing and, consequently, contact means serving the purpose of establishing contact between the shielding plates and the apparatus housing has to be provided.
A further problem relating to the technique of providing separate shielding plates soldered on to the circuit board and encasing the electronic circuits also mounted thereon originates from the trend to mount more and more components on the circuit board by arranging components on both sides thereof and soldering the components on to the circuit board in automatized processes such as dip soldering processes or wave soldering processes in which the entire circuit board having all components arranged on both sides thereof is soldered. When employing these automatized soldering processes, the above shielding plates have to be arranged on the side of the circuit board opposite to the side from which the solder is supplied as the individual compartments defined by the shielding plates would be filled out with solder in case it is attempted to supply solder to the side of the circuit board on which the shielding plates are mounted.
In U.S. Pat. No. 4,370,700, it has been suggested to provide a housing having integrally formed perpendicular walls extending outwardly from the housing into the inner space thereof and to arrange the printed circuit board in abutting engagement with the perpendicularly extending walls so that the circuit board is positioned parallel with the base of the housing and the perpendicularly extending walls encircle the circuits which are located on the board and which are to be shielded. However, the shielding effect is highly dependent on the close abutting arrangement of the circuit board relative to the perpendicularly extending walls. Thus, even a minor gap between the outer side surface of the circuit board and the perpendicularly extending wall of the housing may cause deteriorating leakage which to a grreat extent reduces the desired shielding effect. Furthermore, as the shielding walls are arranged on one side of the circuit board exclusively, the shielding effect is reduced as compared to the technique involving individual encasings, enclosing the individual electronic circuits to be shielded.
In German published patent application Nos. DE-OS 34 45 161 and DE-OS 34 47 347, a housing for an electronic apparatus is disclosed. The housing is assembled from thin metal plates which are assemlbed into a rectangular framework further comprising a base plate and a top plate. Within the housing, a circuit board is arranged which is provided with an elongated aperture through which a shielding plate extends. The shielding plate is a thin metal plate component which is of a configuration comprising a central portion and two bent end portions. The bent end portions are adapted to provide electrical contact to the base plate and the top plate of the housing. In order to establish good electrical contact between the shielding components of the housing and further to the circuit board, the circuit board is soldered to the inner wall of the framework and the shielding plate is soldered to the circuit board. Like the above described technique of Swedish Pat. No. 75 108 00-1 the electronic apparatus assembly of these published German patent applications cannot be soldered in an automatized soldering process, such as a dip soldering process or a wave soldering process as the solder would fill out the inner space of the frame or at least part thereof and consequently provide short-circuiting connections between the housing and the circuit tracks or components of the circuit board, and possibly also between the shielding plate and the circuit tracks or components. Furthermore, the soldered connections between the circuit board and the inner wall of the framework and between the shielding plate and the circuit board renders it very difficult to service the electronic apparatus. The technique of the above German published patent applications is, therefore, applicable only for electronic apparatus which is not serviced but simply replaced by an alternative electronic apparatus in case of malfunction or failure.
Therefore, it is an object of the present invention to provide an apparatus of the above described type in which a single electronic circuit board including the electronic circuits is provided and in which the electronic circuits to be shielded from each other are effectively shielded from each other and from the environment or surroundings.
A further object of the present invention is to provide an apparatus of the above described type which may be manufactured by employing automatized processes, such as dip soldering processes or wave soldering processes and which further renders it possible to service the electronic apparatus by demounting the housing, replacing electronic components of the circuit board and reassembling the housing including the circuit board.